Chapter 14 HO

Padernsof sevendierentcharactersinpea plants

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Unformatted text preview: rait! White!flower!color!is!a!recessive!trait! Key$Points:$$Mendel!experiments! observed!the!inheritance!paderns!!of! seven!different!characters!in!pea! plants! ! ! *! Mendel’s$Model:$note:!!we!will!use!“gene”!where!Mendel!used!“heritable!trait”! ! 1.!!Alterna%ve!version!of!genes!(alleles)!accounts!for!varia%ons!in!inherited!characters! Locus!=!loca%on!where!gene!is! found!on!chromosomes! 2.  For!each!character,!an!organism!inherits!two!alleles;!one!from!each!parent! Alleles!may!be!iden%cal!(e.g.!true!breeding!P!Genera%on)! Alleles!may!be!different!(e.g.!F1!hybrids)! ! 3.  If!the!two!alleles!at!a!locus!differ:! •  The!dominant)allele!determines!the!organism’s!!appearance.!(e.g.!purple!flower!in!F1!hybrid! is!dominant)! •  !!!!! 4.!!Law)of)Segrega<on:!!The!two!alleles!for!a!heritable!character!segregate!during!gamete! forma%on!and!end!up!in!different!gametes!! Gene/c$Vocabulary$ Phenotype:!observable!trait!(purple!or!white)!! Can!also!be!a!physiological!trait!! (self!pollina%on!or!non!self!pollina%on)! Genotype:!gene%c!makeup!(PP!or!pp)!! ! Homozygous:))Two!iden%cal!alleles!for!a!gene!(PP!or!pp)! ! Heterozygous:))Two!different!alleles!for!a!gene!(Pp)! ! ! Two$alleles$segregate$(Mendel’s$Law)! PunneC)Square:))Tool!used!to!make!predic%ons!about!offspring! ) Phenotype:))) Genotype:) ! Dominant)Allele:)!Only!one!copy!is!necessary!for!phenotypic! expression! Recessive)Allele:!!! If$you$had$a$purple$flower,$how$would$you$determine$if$it$was$homozygous$(PP)$or$ heterozygous$(Pp)?$ ! *$ cross testing $ Unknown!Genotype! Known!Genotype! *! Predic<on:) Cross$Test$was$developed$by$Mendel$–$s/ll$an$important$gene/c$tool$ Mendelian genetics: no linkage, very simple, two alleles Mendel$derived$the$first$law,$the$law$of$segrega/on,$from$monohybrid$experiments$ !Alleles segregate = first law In!these!experiments!he!followed!a!single!character!such!as!flower!color! ! All!F1!progeny!in!his!cross!of!true!breeding!parents!were!heterozygous!for!one!character! homozygous for the trait (either dom or rec) ! $ Mendel$derived$the$second$law$of$inheritance$from$dihybrid$crosses$ ! *! In these experiments, he followed TWO characters @ the same time (ex: seed color AND seed shape) ! ! Seed!color:!!yellow!(Y!=!dominant)!or!green!(y!=!recessive)! ! Seed!shape:!!round!(R!=!dominant)!or!wrinkled!(r!=!recessive)! Mendel!was!lucky!when!he!conducted!these!crosses!because!these!characters!are!found! on!different!chromosomes!or!act!like!they!are!on!different!chromosomes! This is really important….if they had been on the same chromosome, the data would not have been so simple ! It wouldve meant they were linked!!!...
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